Electromagnetically operable valve

ABSTRACT

An electromagnetically operable valve having a core on which a magnet coil is arranged, an armature which acts on a valve closing body by means of a connecting pipe, in which the components to be welded together include a reduced diameter portion in which welding of the parts is by a laser in the reduced diameter portions.

PRIOR ART

The invention is based on an electromagnetically operable valve. Anelectromagnetically operable valve has already been proposed in GermanPatent Application P 38 25 135.3, U.S. Pat. No. 4,967,966 in whichsoldering or welding of the armature to the connecting pipe, of theguide element to the core and to the connecting part, of theintermediate part to the core end and to the connecting part, and of theconnecting part to the valve seating body are carried out. Because ofthe space requirement to be provided for the soldering or welding seams,the valve manufactured in this way has a large installed volume. Duringwelding, there is a risk of the parts to be welded to one anotherdeforming because of thermally induced stresses, but also of thenecessary reliability of the connection not being ensured in the case ofrelatively large wall thicknesses of the parts which project over oneanother.

ADVANTAGES OF THE INVENTION

The valve according to the invention, has the advantage that reliablewelding can be achieved and that the valve can be manufactured withrelatively small dimensions in the radial and axial direction. Thesimplified welding in a reduction in cross-section permits a reductionin the heating of the parts to be welded and at the same time forms asafe and reliable connection. Deformation of the parts because of thetemperature effect is thus largely prevented.

Advantageous developments and improvements of the valve specified arepossible by means of the measures outlined hereinafter.

It is particularly advantageous to construct the reduction incross-section as a welded groove which lies in the vicinity of one endof a part to be welded and is bounded at this end by a reinforcingcollar. The welded groove according to the invention is not only easy toproduce but the reinforcing collar is used at the same time asprotection for the welded seam and the small wall thickness in theregion of the reduction in cross-section. The position of the weldedgroove and hence also of the welded seam in the vicinity of the ends ofthe one part to be welded ensure a reliable connection.

It is also advantageous if the reinforcing collar has an insertion stageand/or a chamfer towards a central opening, in order to facilitateeasier pushing together of two cylindrical or pipe-shaped parts whichare to be welded to one another.

It is likewise advantageous if the valve seating body has acircumferential groove between the valve seat and a welded seamconnecting the valve seating body to the connecting part. This reductionin the cross-sectional area reduces the heat flow during welding fromthe welded seam into the valve seat of the valve seating body, so thatwarping of the valve seat as a result of thermally induced stresses isprevented.

In this case it is advantageous if the cross-sectional area of the valveseating body between a treatment hole in the valve seating body and agroove base of the circumferential groove is less than one quarter ofthe cross-sectional area of the valve seating body which is formedbetween the contact line of the valve closing body resting against thevalve seating area and the circumference of the valve seating body, inorder to reduce the heat flow as much as possible, but withoutendangering the stability of the valve seating body.

It is particularly advantageous if the wall thickness of the reductionin cross-section of the one part to be welded is approximately 0.3 mm inthe region of the weld, so that, on the one hand, a reliable weld isensured, but on the other hand only a reduced heat supply is requiredduring welding, because of the reduced wall thickness.

It is also advantageous if the wall thickness of the reduction incross-section of the one part to be welded is significantly less thanthe wall thickness of the other part to be welded in the region of theweld, so that a reliable weld and the necessary heat dissipation areensured by the considerably greater wall thickness of the other part.

It is particularly advantageous to provide a hollow identificationelement, which is manufactured from plastic, engages around the valveand is held thereon. The coloured configuration of the identificationelements of valves allows rapid identification of the valve type duringproduction, assembly or during storage of spare parts.

DRAWING

An exemplary embodiment of the invention is shown in simplified form inthe drawing and is explained in detail in the following description.

FIG. 1 shows an exemplary embodiment of a valve designed according tothe invention and

FIG. 2 shows the welding according to the invention of two metallicparts of the valve which project over one another.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

The electromagnetically operable valve, which is shown for example inFIG. 1, in the form of an injection valve for fuel injection systems ofinternal-combustion engines has a core 1, which is surrounded by amagnet coil 3, is of pipe-shaped construction, and via which the fuel issupplied. A first connecting section 5, surrounding the core end 2, of apipe-shaped metallic intermediate part 6, which has a reduction 40 incross-section on the circumference, is connected by a welded seam 54,which runs in the reduction 40 in cross-section and is produced by meansof a laser, in a sealed manner to the core 1, concentrically withrespect to a valve longitudinal axis 4 and adjacent to a lower core end2 on which the magnet coil 3 is arranged.

The weld according to the invention which is shown in FIG. 2 of twometallic parts of the valve projecting over one another is intended toapply to all welds of the valve in a suitably adapted form and shows, byway of example, the reduction 40 in cross-section, constructed as awelded groove, of the first connecting section 5, which reduction incross-section is located in the vicinity of one end of the part, forexample the intermediate part 6, and is bounded at this end by areinforcing collar 41 which extends radially beyond the groove base. Thereinforcing collar 41 is used as protection for the welded seam 54 andthe small wall thickness of the reduction 40 in cross-section, ofapproximately 0.3 mm. If the reinforcing collar 41 has an insertionstage 42 and/or a chamfer towards the central opening 55 of theintermediate part 6, this makes assembly easier. The wall thickness ofthe other part to be welded, which is considerably greater than that ofthe reduction 40 in cross-section, in this case of the core end 2,permits a safe and reliable weld.

A second connecting section 7 of the intermediate part 6, which has agreater diameter than the first connecting section 5, engages around apipe-shaped metallic connecting part and is connected thereto by meansof a laser weld corresponding to the representation in FIG. 2, which isdesigned in a reduction 50 in cross-section which is constructed at thedownstream end of the second connecting section 7. In order to makesmall external dimensions of the valve possible, the first connectingsection 5 engages around a retaining step 36 of the core end 2, whichhas a smaller external diameter than the core 1, and the secondconnecting section 7 engages around a retaining step 37 of theconnecting part 20, which is likewise constructed with a smallerexternal diameter than in the adjacent region.

A valve seating body 8, having a groove 31, is welded into a retaininghole 39 at the end of the connecting part 20 facing away from the core1, the weld, which is produced by means of a laser, running in areduction 52 in cross-section of the connecting part 20, as is shown byway of example in FIG. 2. In this case, the groove 31 lies between thevalve seat 9 and the reduction 52 in cross-section. The juxtaposition ofthe core 1, the intermediate part 6, the connecting part 20 and thevalve seating body 8 thus represents a compact, rigid metallic unit. Atleast one spray opening 17 is constructed in the valve seating body 8downstream from the valve seat 9.

A displacement sleeve 22, which is pressed into a flow hole 21 of thecore 1, is used for setting the spring pretension of a restoring spring18 which rests against the displacement sleeve 22 and is supported on aconnecting pipe 23 by means of its end which points downstream. Anarmature 12 is connected by laser welding to the end of the connectingpipe 23 facing the restoring spring 18, in the reduction 51 incross-section of which armature, constructed facing away from the coreend 2, a welded seam runs corresponding to that shown in FIG. 2. Thepipe-shaped intermediate part 6, with a guide collar 10, is at the sametime used as a guide for the armature 12. At the other end of theconnecting pipe 23, said connecting pipe is connected to a valve closingbody 14 for example by welding, which is constructed for example as asphere and interacts with the valve seat 9.

The circumferential groove 31 in the valve seating body 8 results in thecross-sectional area of the valve seating body 8 between a treatmenthole 32 of the valve seating body 8 and a groove base 33 of thecircumferential groove 31 being less than one quarter of thecross-sectional area of the valve seating body 8 which is formed betweenthe contact line of the valve closing body 14, which rests against thevalve seating area, and the circumference of the valve seating body 8.This reduced cross-sectional area reduces the heat flow during weldingfrom the welded seam 30 into the valve seat 9, so that warping of thevalve seat 9 as a result of thermally induced stresses is prevented.

The magnet coil 3 is surrounded, completely in the axial direction andat least partially in the circumferential direction, by at least oneguide element 28, which is used as a ferromagnetic element and isconstructed in the exemplary embodiment as a clip. The guide element 28is matched by means of its region 29 to the contour of the magnet coil3, an upper end section 44 which extends radially inwards engagespartially around the core 1, a lower end section 45 engaging partiallyaround the connecting part 20. The upper end section 44 is connected bymeans of its end facing away from the valve closing body 14 to the core1 by means of laser welding, the weld being constructed in a singlereduction 46 in cross-section of the upper end section 44 running overonly a part of the circumference of the guide element 28. The guideelement 28 is connected by means of its lower end section 45 to theconnecting part 20 in a reduction 47 in cross-section, by means of laserwelding, for example corresponding to the weld shown in FIG. 2. Sincethe guide element 28 does not carry out any sealing function, acircumferential, sealed weld is not required, so that the reductions 46,47 in cross-section on the upper end section 44 and the lower endsection 45 also do not need to be constructed circumferentially. In afurther exemplary embodiment, not shown here, it is also possible, inthe same way as on the upper end section 44, to dispense with theconstruction of a welded groove running over the entire circumference ofthe guide element 28, on the lower end section 45 as well, and toprovide only a single reduction in cross-section extending over only apart of the circumference of the guide element 28.

At least one part of the core 1 and the magnet coil 3 over its entireaxial length are surrounded by a plastic sheath 24 which also surroundsat least the intermediate part 6 and a part of the connecting part 20. Apipe-shaped identification element 27, which partially surrounds theconnecting part 20, is manufactured from coloured plastic and is held onthe valve by a clamp, press or screw connection, is connected to saidplastic sheath 24, which is produced by filling out or extrusion coatingwith plastic. The coloured identification of the valve permits rapididentification of the valve type during production, assembly or duringstorage of spare parts.

At the same time, an electrical connecting plug 26 is integrally formedon the plastic sheath 24, via which electrical contact is made with themagnet coil 3 and said coil is hence energised.

The laser welds according to the invention, which are carried out inreductions in cross-section, not only make a compact construction of thevalve possible but are also distinguished by high safety and reliabilityas well as easy practicability.

The foregoing relates to a preferred exemplary embodiment of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. An electromagnetically operable valve for fuel injectionsystems of internal-combustion engines, having a core (1) surrounded bya magnet coil (3), an armature (12) welded to a connecting pipe (23), avalve closing body (14) which interacts with a fixed valve seat (9) iswelded to said connecting pipe, a core end facing said armature, apipe-shaped metallic intermediate part (6) which is connected by meansof an upper end to said end (2) of said core facing the armature and bymeans of a lower end is connected to a pipe-shaped connecting part (23)in a sealed manner by welding, at least one clip-shaped guide element(29), which engages over the magnet coil and is connected by means of alower end facing the valve closing body to the connecting part (20), andis connected by means of an upper end to the core (1) by welding, ametallic valve seating body (8), which has a fixed valve seat (9), andis mounted on the connecting part (20) on an end facing away from theintermediate part by welding, said lower end of said armature (12)includes a reduced diameter portion in cross section which is welded tosaid connecting pipe (23), said upper and lower ends of saidintermediate part include a reduced diameter portion which is welded tosaid lower end (2) of said core (1) and said connecting part (20),respectively, said upper and lower ends of said clip-shaped guideelement (29) includes a reduced diameter portion which is welded to saidcore (1) and said connecting part (20), respectively, and said lower endof said connecting part (20) includes a reduced diameter portion whichis welded to said valve seating body.
 2. A valve according to claim 1 inwhich said intermediate part includes a reinforcing collar (41)juxtaposed said reduced diameter portion.
 3. A valve as set forth inclaim 2, in which said reinforcing collar includes an insertion stage(42) with a chamfer towards a central opening (55).
 4. A valve accordingto claim 1, in which the valve seating body (8) has a circumferentialgroove (31) between the valve seat (9) and a welded seam (30) whichconnects the valve seating body (8) to the connecting part (20).
 5. Avalve according to claim 2, in which the valve seating body (8) has acircumferential groove (31) between the valve seat (9) and a welded seam(30) which connects the valve seating body (8) to the connecting part(20).
 6. A valve according to claim 3, in which the valve seating body(8) has a circumferential groove (31) between the valve seat (9) and awelded seam (30) which connects the valve seating body (8) to theconnecting part (20).
 7. A valve according to claim 4, in which thecross-sectional area of the valve seating body (8) between a treatmenthole (32) in the valve seating body (8) and a groove base (33) of thecircumferential groove (31) is less than one quarter of thecross-sectional area of the valve seating body (8) which is formedbetween the contact line of the valve closing body (14) resting againstthe valve seating surface and the circumference of the valve seatingbody (8).
 8. A valve according to claim 5, in which the cross-sectionalarea of the valve seating body (8) between a treatment hole (32) in thevalve seating body (8) and a groove base (33) of the circumferentialgroove (31) is less than one quarter of the cross-sectional area of thevalve seating body (8) which is formed between the contact line of thevalve closing body (14) resting against the valve seating surface andthe circumference of the valve seating body (8).
 9. A valve according toclaim 6, in which the cross-sectional area of the valve seating body (8)between a treatment hole (32) in the valve seating body (8) and a groovebase (33) of the circumferential groove (31) is less than one quarter ofthe cross-sectional area of the valve seating body (8) which is formedbetween the contact line of the valve closing body (14) resting againstthe valve seating surface and the circumference of the valve seatingbody (8).
 10. A valve according to claim 1, in which the wall thicknessof the reduced diameter portions in cross-section is approximately 0.3mm.
 11. A valve according to claim 2, in which the wall thickness of thereduced diameter portions in cross-section is approximately 0.3 mm. 12.A valve according to claim 3 in which the wall thickness of the reduceddiameter portions in cross-section is approximately 0.3 mm.
 13. A valveaccording to claim 4, in which the wall thickness of the reduceddiameter portions in cross-section is approximately 0.3 mm.
 14. A valveaccording to claim 7, in which the wall thickness of the reduceddiameter portions in cross-section is approximately 0.3 mm.
 15. A valveaccording to claim 10, in which the wall thickness of the reduceddiameter portions in cross-section of the one part to be welded issignificantly less than the wall thickness of the part without a reduceddiameter.
 16. A valve according to claim 1, in which said valve includesa hollow identification element (27), which is manufactured from plasticand which engages around the valve and is held thereon.
 17. A valveaccording to claim 2, in which said valve includes a hollowidentification element (27), which is manufactured from plastic andwhich engages around the valve and is held thereon.
 18. A valveaccording to claim 3, in which said valve includes a hollowidentification element (27), which is manufactured from plastic andwhich engages around the valve and is held thereon.
 19. A valveaccording to claim 4, in which said valve includes a hollowidentification element (27), which is manufactured from plastic andwhich engages around the valve and is held thereon.
 20. A valveaccording to claim 7, in which said valve includes a hollowidentification element (27), which is manufactured from plastic andwhich engages around the valve and is held thereon.
 21. A valveaccording to claim 10, in which said valve includes a hollowidentification element (27), which is manufactured from plastic andwhich engages around the valve and is held thereon.
 22. A valveaccording to claim 15, in which said valve includes a hollowidentification element (27), which is manufactured from plastic andwhich engages around the valve and is held thereon.